1. Field of the Disclosure
The disclosure relates in general to a phase-locked loop system.
2. Description of the Related Art
Phase-locked loop systems are widely used in analog and digital circuits. Typically, such systems may include a phase frequency detector, a charge pump, and a voltage-controlled oscillator (VCO). In a phase-locked loop system, the VCO is used to generate an output signal whose frequency is gradually close to and ultimately locked on a target frequency that is obtained according to a reference signal of the phase frequency detector. Even the phase-locked loop system has the output signal and the reference signal matched in frequency or phase, noises such as frequency or phase jitter still exist in the output signal. Therefore, it is a subject of the industrial endeavors to provide a phase-locked loop system which can minimize or reduce jitter.